Section 214.20. Soil investigation requirements.

 

(1)   Applicability. This section is applicable to all new, expanded or modified land treatment systems receiving liquid wastes, by-product solids and sludges from industrial facilities for which a plan approval under s. 281.41 , Stats., and ch. NR 108 or a WPDES discharge permit under ch. 283 , Stats. , is required. It is also applicable to those existing dischargers which need to demonstrate according to s. NR 214.06 (1) that their land treatment system complies with groundwater protection requirements although the system does not meet each specific design standard.

(2)   Professional qualifications. The department shall accept soil test pit evaluations, soil classifications and soil boring logs performed by a qualified soil scientist, engineer or other qualified individual. Qualifications shall include a degree from an accredited institution of higher education or field experience in soil investigation, interpretation and classification.

(3)   Technical procedures. All technical procedures used to investigate a wastewater disposal facility shall be the current standard procedures as specified by the American society for testing and materials, United States geologic survey, standard methods for the examination of water and wastewater, or other equivalent or appropriate methods approved by the department. Test procedures used shall be specified. Any deviation from a standard method shall be explained in detail with reasons provided.

(4)   Soil evaluations for landspreading and sludge spreading systems. The following soil related information shall be submitted for sludge spreading systems or landspreading systems for liquid waste or organic by-product solids:

(a) Individual treatment site locations identified on topographic maps, plat maps or aerial photographs,

(b) Relevant, existing soil survey information such as that assembled by the U.S. department of agriculture, soil conservation service including the soil names, percent slope, relative permeability, available water capacity, organic matter content and current land use,

(c) A detailed soils map displaying the location of the various soils on the site at a scale of not more than 2,000 feet to the inch,

(d) Laboratory determined or estimated soil cation exchange capacity,

(e) Agronomic soil nutrient testing results for making fertilizer and liming recommendations for cover crop growth using procedures such as those employed by the university of Wisconsin - cooperative extension program,

(f) Additional soil related information that may be required by the department on a case-by-case basis.

(5)   Treatment systems where groundwater monitoring wells are not required. For absorption pond, ridge and furrow, spray irrigation, overland flow and subsurface absorption systems where groundwater monitoring wells are not required, or for those sites which are being investigated for potential future use as such systems, the soils evaluation shall contain the following information and investigation, at a minimum:

(a) The location, soil survey, soil cation exchange capacity and soil nutrient content information as specified for landspreading systems in sub. (4) .

(b) A sufficient number of soil test pits shall be excavated to adequately define the soil conditions found on the site.

1. Prior to soil test pit construction, the treatment site owner or operator and the department shall agree on the number and location of test pits to be excavated dependent upon the size of the land treatment site and uniformity of soils and geology.

2. The soil test pits shall be large enough to allow visual inspection and documentation of soil layers and shall be excavated to a depth of 5 feet below the final base grade of the system. The U.S. occupational health and safety administration requires that test pits with more than 5 feet of standing wall shall not be entered unless provision is made to prevent caving of the walls.

3. The department shall be notified at least 24 hours prior to excavation of the soil test pits to allow inspection by department personnel.

(c) Soil samples from the test pits shall be collected and analyzed at each significant change in soil characteristics or lithology for the following:

1. Soil textural classification in accordance with the unified soil classification system as specified in ASTM standard D-2487-85.

2. Particle size analysis performed in accordance with ASTM D422-72 to determine particle size distribution. With department approval, soil samples may be composited, or the particle size determined by a sieve analysis to reduce repetitive testing of similar soil samples.

3. The soil moisture holding capacity by direct measurement or as specified through reference to literature values for different soil textures.

(d) Following soil sample collection, the test pits shall be deepened to the extent practical with a backhoe to check for bedrock, the water table or for soil layers that would restrict the downward movement of water. This shall be visual check from the land surface, unless the test pits are protected from caving in accordance with U.S. occupational safety and health administration requirements. All soil test pits shall be refilled with excavated material following deepening for the bedrock, water table and impervious layer check.

(6)   Treatment systems with required groundwater monitoring. For land treatment systems where groundwater monitoring wells are required, the soils evaluation shall contain the following information and investigation, at a minimum:

(a) A preliminary site investigation report shall be assembled that contains the site location, soil survey, soil cation exchange capacity and soil nutrient content information as specified for landspreading systems in sub. (4) . Also, a limited number of test pits may be constructed to provide preliminary soils information, such as that specified in sub. (5) .

(b) The treatment system owner or operator shall submit the results of the preliminary site investigation and propose a full scale treatment site investigation plan.

(c) The full scale treatment site investigation shall consist of a combination of soil test pits and soil borings to adequately define the soil, groundwater and bedrock conditions at the site.

1. Prior to construction of test pits and soil borings, the treatment site owner or operator and the department shall agree on the number and location of soil borings and test pits dependent upon the size of the site and uniformity of soils and geology.

2. The soil test pits shall be investigated as specified in sub. (5) .

3. The soil sampling in borings shall be performed in accordance with ASTM D1586-84 or ASTM D1587-83.

4. The soil borings shall extend to the groundwater table, be terminated upon encountering bedrock, or be drilled to a minimum depth agreed upon in the preliminary site investigation plan. The department may require the borings to extend to a minimum depth of 25 feet below the final base grade of the land treatment system when groundwater or bedrock is not encountered first.

(d) Soil samples which are above the normal groundwater level and are contained in the unsaturated zone shall be collected from the test pits and soil borings and analyzed at each significant change in soil characteristics or lithology as specified in sub. (5) (c) . Hydrogeologic testing requirements are specified in s. NR 214.21 (2) (e) .

(7)   High rate absorption pond systems. For absorption pond systems having a design hydraulic application rate greater than 10,000 gpd/acre, the minimum soil, groundwater and bedrock related information and requirements are those listed in sub. (6) , with the following additional requirements:

(a) At least 2 saturated hydraulic conductivity tests shall be performed on the soils located at the final base grade of the system using a field permeability test. In some cases, the department may allow laboratory permeability tests on hydrated and saturated samples compacted at the same approximate density as exists in the in-field condition. These laboratory tests may be performed on molded or core samples, and separate tests shall be performed using tap water, wastewater or sludge extract. The permeability shall be based on stabilized inflow and outflow rates during the test. All preparation work and information detailing the test apparatus shall be submitted along with all results obtained.

(8)   Data presentation. The results from the subsurface investigation shall be presented in accordance with ch. NR 108 as follows:

(a) Existing site conditions and surrounding natural and man-made conditions shall be presented on a baseline topographic map.

(b) Cross-sections shall be developed and presented to illustrate subsurface geologic and geomorphic conditions. At least one cross-section shall be developed parallel to groundwater flow. The cross-sections shall present documented and inferred stratigraphic, soil, groundwater and bedrock conditions of the site. Soil test pit and soil boring information shall be correlated to each cross-section developed.

History: Cr. Register, June, 1990, No. 414 , eff. 7-1-90; am. (5) (c) 1., Register, April, 1991, No. 424 , eff. 5-1-91.